Beijing - China on Friday confirmed that two police officers were stabbed to death and five others were injured during the latest in a series of attacks in the restive Central Asian region of Xinjiang.

The officers were "investigating a previous case" when they were ambushed by attackers who were hiding in a cornfield on Wednesday night in Xinjiang's Jiashi county, the official Xinhua news agency quoted a police spokesman as saying.

Police were investigating the attack, the agency said without giving any further details.

The German-based World Uighur Congress reported the deaths on Thursday and said at least 20 people were arrested following the attack in Jiashi, which is about 100 kilometres east of China's westernmost city of Kashgar.

The group said earlier this week that Chinese police had detained 500 Uighurs in the Xinjiang region over the past two weeks. More than 100 people were also arrested in Kashgar after an August 4 attack that killed 16 paramilitary officers in the city, it added.

The August 4 attack, which China said was carried out by two Uighur men, was among a string of deadly assaults carried out against government, police and security personnel in Xinjiang before and during this month's Beijing Olympic Games.

At least 26 people were killed in a 10-day period.

Human rights groups have criticized China for not making a distinction between violent terrorists and Uighurs expressing peaceful dissent, including those who favour independence, which they said should not be a crime.

The Uighur group said earlier that about 90 people were arrested after a series of bombings in Kuqa county on August 10. Ten "terrorists" were killed by police bullets or their own bombs, the government said. (dpa)